Ya id prob say 155, im 6ft 135lbs and thats what I have and I ride pretty much everything. My roomate has the 151 but he's shorter than me by a bit. Especially since you said you almost never hit the park your gonna gain more from the extra stability of a longer board vs the easier maneuverability of the shorter one. Not that 155-153 is gonna make a HUGE difference...

Go with the longer board. You're not in the park. You'll have more stability and better flotation in powder with a long board. The benefits of the longer board will greatly outweigh the slightly less maneuverability.

I bought a 158 SL at the end of the season last year after demoing a bunch of boards. I demoed the 158 Legacy, but it's what they had to demo. You'll notice a huge difference in performance from the noodly Evo to the SL. I did a similar transition.